PROJECT SUMMARY/ABSTRACT Long emergency department (ED) wait times resulting from overcrowding occur on a daily basis in 10% to 30% of hospitals and at least once per week in 90% of hospitals. It is widely acknowledged that long wait times are correlated to poor health outcomes due to lack of timeliness and inability to administer treatment. While there are many causes of prolonged ED wait times, a predominant source is the high demand for radiology services, which provide 47 million X-rays to US EDs each year. While many X-rays are often performed for patients with time critical conditions, ~17 million are acquired for patients with suspected bone fractures, 50% of which are ?routine? in bones with simple geometries. In addition to delays caused by radiology backlog, acquiring an X-ray in the ED is resource and time consuming. This process typically involves the following: arrange time on the X-ray machine, transport the patient to the X-ray machine, acquire the X-ray image(s), transport the patient and image results back to the ED, acquire a disposition from the radiologist, and communicate disposition to the ED or orthopedic physician. Each ED-ordered X-ray consumes > 30 minutes with an additional > 30 minutes to acquire a radiologist disposition. The total cost of this process to the US healthcare system is an estimated $3.2B. During the Phase I project, the feasibility of a 3D ultrasound imaging system and new technologies was demonstrated in an ex vivo bone fracture model. The 3D ultrasound images were reviewed by two independent ED physicians who detected bone fractures with 100% sensitivity and 96% specificity. This Phase II proposal seeks funding to support the continued development of a 3D ultrasound imaging system for bone fracture detection. The key technological innovations of this project are focused on improvements to ultrasound-based bone visualization and include a new clinician-assist feature that enables automatic detection of suspected bone fractures. The long-term goal of this project is to demonstrate a 3D bone-imaging ultrasound system that facilitates the rapid detection of bone fractures, expedites care delivery within the Emergency Department, and lowers the risk of health complications associated with delays in treatment delivery. The Phase II hypothesis is that the 3D ultrasound bone imaging system will exhibit substantially equivalent sensitivity and specificity as digital X-ray for the detection of fractures in patients presenting to the Emergency Department with suspected long bone fractures. Novel ultrasound imaging technologies central to this project will be optimized, integrated into the 3D ultrasound bone imaging system, and validated in both post-mortem human subjects and human clinical studies. Finally, the Phase II hypothesis will be tested in a 135 patient clinical study. With an estimated 8.5 million suspected bone fracture cases in approximately 5,000 EDs across the US each year, the estimated US market size for this proposed ultrasound imaging device is $200 M/yr.